Keypad scanning with radio event isolation

ABSTRACT

Apparatus and methods for scanning a keypad of a communications device in a manner that tends to minimize interference with transceiver operation, such as a RF transceiver. In one embodiment, a controller receives a periodic signal of the communications device and provides a scan signal to cause the keypad to be scanned. In a sleep mode a keypad scan is performed only subsequent to a keypad activation. However, if the communications device is in use a keypad scan is performed once per frame at predetermined intervals, in one embodiment.

FIELD OF THE INVENTION

The invention relates generally to the design and operation ofcommunications equipment and, more particularly, to a technique tominimize interference with transceiver operation that may be occasionedwhen a user device, such as a keypad, is scanned to determine the statusof a user input.

BACKGROUND

In many types of mobile communications equipment, including wirelesscommunications equipment such as a cellular telephone, user inputs areentered through the operation of a keypad. The keypad is conventionallyconstructed in the form of a crosspoint switch, wherein individual keysoccupy respective nodes of an array that constitutes the keypad.Information from and to the user is conveyed through the keypad array inthe course of keypad scanning procedure. The scanning procedure mostfrequently incorporates a debounce algorithm that is calculated tovalidate perceived key activations. The keypad is perhaps the mostgeneral user input that is recognized by the communications equipment.(Those skilled in the art will understand that embodiments of theinvention are applicable to myriad forms of communications equipment, ofwhich the cellular telephone is but a salient example. Accordingly, theterm “equipment” or “communications equipment” is intended here toinclude not only cellular telephones, but all types of user-operatedequipment that comprise a user input device and that operateconcurrently with the receiving or transmitting of a signal such as aradio frequency (RF) signal). In general, a keypad scanning procedurerequires that outputs from the baseband be passed through the keypadarray and subsequently returned to the baseband to determine whether anykey has been depressed, or otherwise “selected” by the user.

In the context of an integrated transceiver, such as a single chipcommunications terminal (i.e., a device that is designed and implementedso that both RF (radio frequency) and baseband functions and circuitryreside on the same integrated circuit (IC)), the suppression of digitalswitching noise and the minimization of current loops are designaspirations. Conventional keypad scanning techniques distribute currentfrom baseband circuitry to the uncontrolled large area occupied by thekeypad array, and then back to the baseband. The activation of suchlarge current loops during the presence of RF activity creates thepotential for the keypad activity to interfere with the radioperformance. As performed in this manner, keypad scanning isantithetical to the objective of limiting current loops.

Irrespective of the manner in which it is accomplished, the eliminationof current loops during intervals when the RF transceiver is inoperation (sometimes referred to herein as a “radio event”) persists asa prevailing design objective in an integrated transceiver. The digitalinterference generated by the keypad scanning activity, which will beresponsible to power up large areas of a system circuit board, tends toadversely affect the performance of the RF transceiver. Keypad arraysare commonly designed to apply power to all the array outputs until akeypress is detected, in the course of a keyscan process, for example.

Accordingly, there persists a need, particularly in integrated singlechip communications terminal architectures, to isolate the keypadscanning procedure from radio events, e.g., during the reception ortransmission of an RF signal. In addition, in providing radio eventisolation during a keypad scanning procedure, deference must be paid toexisting keypad scanning techniques. In particular, it is preferred thatenhancements effecting radio event isolation during keypad scanning bedownward compatible with equipments that are configured to includeseparate (i.e., non-integrated) transceiver and baseband blocks. Forexample, it is desired that keypad debouncing be accomplished insubstantially the prevailing manner.

SUMMARY OF THE INVENTION

In one aspect, the invention inheres in a keyscan isolation apparatusincludes a keyscan controller to receive to a periodic signal that isprovided in a communications device to establish operation of thecommunications device. The keyscan controller has an output to provide asignal to couple to a keypad interface device to cause a keypad to bescanned.

In another aspect, a method of scanning a keypad for a communicationsdevice includes detecting the occurrence of a signal (e.g., a FRMStrobe) that is provided to the communications device to establish anaspect of operation of the device. In response of the occurrence of thesignal, a keypad debounce procedure is performed.

In a further aspect, a keyscan isolation apparatus includes a keyscancontroller having a first input to couple to a periodic signal that isprovided to a communications device to establish operation of thecommunications device. The keyscan controller has an output to provide asignal to couple to a keypad interface device to cause a keypad to bescanned. The apparatus also includes a counter having an input coupledto a clock signal (CLK), a first output coupled to the keyscancontroller to cause the keyscan controller to provide a signal to thekeypad interface device, and a second output to couple to the keypadinterface device to establish a predetermined condition at an output ofthe keypad interface device.

In a still further aspect, a storage medium may include instructions todetect the occurrence of a FRM Strobe signal and to perform a keypaddebounce procedure within an interval that is short with respect to aperiod of the FRM Strobe signal.

In yet another aspect, a communications system includes an RFtransceiver; a baseband stage coupled to the transceiver; a keypadinterface to couple to a keypad to perform a keyscan procedure on asystem keypad; and a keyscan isolation device coupled to the basebandstage and to the keypad interface. The keyscan isolation device, inturn, includes a keyscan counter having a clock input to controllablycouple to a clock, and a reset input to couple to a system signal thatestablishes an aspect of the operation of the system. The keyscanisolation device also includes a keyscan controller having an inputcoupled to a first output of the counter and an output coupled to thekeypad interface device to execute a keyscan procedure in response tothe counter output.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject keypad scanning technique with radio event isolation may bebetter understood by, and its many features, advantages and capabilitiesmade apparent to, those skilled in the art with reference to theDrawings that are briefly described immediately below and attachedhereto, in the several Figures of which identical reference numerals (ifany) refer to identical or similar elements, and wherein:

FIG. 1 is a high-level diagram of an embodiment of the invention.

FIG. 2 is a conceptual representation of a keypad array, underscoringthe significance of KeyIn and KeyOut signals.

FIG. 3 is a high-level diagram in accordance with an embodiment of theinvention in which keypad scanning is achieved with a reduction in powerconsumption.

FIG. 4 is a timing diagram that illustrates the relationships amongvarious significant waveforms that are encountered in a hypotheticalkeypad scanning procedure.

FIG. 5 is a high-level diagram of a transceiver system in accordancewith an embodiment of the invention.

Skilled artisans appreciate that elements in Drawings are illustratedfor simplicity and clarity and have not (unless so stated in theDescription) necessarily been drawn to scale. For example, thedimensions of some elements in the Drawings may be exaggerated relativeto other elements to promote and improve understanding of embodiments ofthe invention.

DETAILED DESCRIPTION

For a thorough understanding of the subject invention, reference may behad to the following Detailed Description, including the appendedClaims, in connection with the above-described drawings. Principally forpurposes of precision and concision, embodiments of the invention aredescribed here in the context of keypad scanning that is performed on acellular telephone, although the scope of the present invention is notso limited. In particular, for reasons that will become clear below,particular reference is made to the GSM (Global System for MobileCommunications) as exemplary of the numerous types of communicationsystems with which embodiments are compatible. However, a skilledartisan will understand that the invention is not constrained in itsapplicability to wireless communications devices generally, much less tocompatibility with GSM standards and or protocols.

The subject technique for effecting keypad scanning enables informationto be extracted from the keypad of a communications device, such as acellular telephone, without generation of interference in the course ofongoing radio events. In an embodiment, keypad scanning is performed inresponse to a system signal that precedes a period during which theremay occur no radio events. The embodiment incorporates aspects thatsimulate the system signal during periods when the communications deviceis dormant. In an alternative embodiment, keypad scanning is performedin a manner that reduces power consumption attributable to the keypadscanning procedure.

In the use of a cellular telephone, for example, the keypad is regularlymonitored to obtain a user input. The user activates a key by the act ofdepressing a selected key on the keypad. Transmission of informationfrom the keypad uses multiple output and input pins on a keypadinterface device. The monitoring operation sequentially monitors thestatus of individual keys to determine which, if any, of the keys mayhave been selected. If a key is determined to have been selected, then acircuit connection is made between the keypad interface device input(from the keypad) and the keypad interface device output (to a basebandcircuit) in order to register a key activation, as evidenced by theelectrical connection of a keyout to a keyin pin of the single chipcommunications terminal through a switch integrated within the keypaddesign. The distribution of keypad information creates a relativelylarge, uncontrolled off-device, circuit path. Because of the physicalarea encompassed by this circuit path, and because of the transientnature of the signals the circuit path conveys, the distribution ofkeypad information in this manner gives rise to significant RF noiseinterference concerns.

Under normal baseband conditions, in response to the identification ofkeypress event, keypad scanning occurs at a predetermined programmedrate, typically an integer time in milliseconds. The keyscan period isgenerally accomplished by dividing a real-time baseband clock, which maytypically run at 32768 Hz (often referred to herein as a 32 kHz clock,or real-time clock, generally). In this manner, a predetermined scanningperiod is established. A scanning signal herein referred to as “RunScan”is thereby provided to scan the keypad.

Conventionally, keypad scan is performed completely in the domain ofbaseband, without regard to any transceiver activity that might then betaking place, generally in a separate, isolated, EMI shielded cavitywithin the cellular handset. That is, conventionally the keypad scanningprocedure is indifferent to a radio event in the form of the receptionor transmission of RF signals by the transceiver of the equipment.However, the generation of interfering noise is a concern while thetransceiver is in operation, and the keypad scanning circuitry isresident on the same die as the RF transceiver, or within the same EMIshielded cavity as the RF transceiver. Therefore, the large circuitcreated during the keypad scan, as well as the transient and noisynature of the scanning signals, is largely incompatible with a low-noisedesign. Furthermore, the situation is exacerbated by the fact that thedesign of the keypad interface circuit itself is rarely informed byinterference abatement considerations. That is, in most commerciallyavailable cellular phone equipment, the keypad interface circuit isgenerally acquired from an OEM (original equipment manufacturer) who hasminimal concern related to noise interference.

One implementation in a device including an RF transceiver and basebandcircuits is to interrupt the operation of the clocks and digitalswitching events while the RF transceiver is in use. In accordance withthis principle, all the keypad interface signals are held at a constantstate during any RF event. During RF activity, the input and outputsignals involved in the keypad activity are held at the same potential.The user is expected to press a key while the radio is in use. Since thekeypad signals are held at a constant state, any key press that occursduring RF activity does not change the state of the signals on the chip,thus eliminating any interference with the RF activity.

In the conception of embodiments of the invention, an initiallyappealing approach causes the keypad scan to occur at a fixed point intime in each GSM frame. However, this approach fails in the case ofextended dynamic allocation, which, in the manner implemented in GSM,countenances the possible utilization of each slot in the GSM frame.Therefore, there appears to exist no predetermined position in a framethat may, with confidence, be dedicated to a keypad scan procedure. Inone embodiment, in order to ensure that a keyscan occurs while thetransceiver subsystem is inactive, a periodic GSM frame signal that isused in the baseband for processing events may be used to trigger akeyscan procedure. In particular, consistent with embodiments describedherein, a GSM Frame Strobe (FRM Strobe) or another suitable signalprecipitates a keyscan procedure.

In the GSM environment, the mobile equipment generates a periodic FRMStrobe signal, approximately every 4.6 ms (milliseconds). In general, inresponse to a FRM Strobe signal that is received in a given frame, thecellular telephone determines what activity will be undertaken in thecourse of the next succeeding frame. The FRM Strobe signal is generatedwhen the phone is communicating with a base-station using the RFinterface, that is, not in a SLEEP (or dormant) state. However, thetiming of the FRM Strobe can be correlated to the period when it isassured that the transceiver subsystem is not engaged in thetransmission or reception of an RF signal. Use of the FRM Strobe totrigger a keyscan procedure performs the keyscan procedure while thetransceiver is inactive. In systems where no such frame rate signalexists, a periodic signal may be added to the system, in a mannersimilar to the frame signal previously described, that allows thekeyscan procedure to operate at known non-RF (i.e., when the transceiveris inactive) times during the GSM Frame.

In addition, in accordance with an embodiment, the keyscan procedure isperformed during intervals in which the equipment is in the SLEEP state.Specifically, it is generally considered unacceptable to stall keypadscanning until the system processor returns from the SLEEP state toaccess the paging channel, or to perform other system functions, anddetermine whether a key has been activated, as the SLEEP state can existfor greater than two seconds. However, during the SLEEP state, the FRMStrobe signal is not present. In addition, it may be the case that theonly system clock available during SLEEP is the 32 kHz clock or realtime clock. But that clock is largely disassociated from the devicewhile the transceiver subsystem is operative. Accordingly, in oneembodiment the keypad scanning procedure is not entirely predicated onthe availability of the 32 kHz clock or real-time clock.

FIG. 1 is a block diagram of an embodiment that provides an effectivekeypad scanning technique. In addition, embodiments of the technique areeffective to isolate the transceiver subsystem from noise interferencethat may derive from the scanning procedure. The embodiment of FIG. 1incorporates, i.e., is responsive to, both the FRM Strobe signal and the32 kHz clock or real-time clock to synthesize a keypad scanning signal(RunScan) that causes a keyscan procedure to be performed. As will beseen with respect to the embodiment of FIG. 1, a keypad scan procedurewill be conducted in response to the FRM Strobe signal when thetransceiver is in use. Otherwise, a keypad scan will be initiated inresponse to the 32 kHz clock or real time clock at periodic intervalsthat approximate the 4.6 ms FRM Strobe period, through the use of a scancounter.

As may be seen in FIG. 1, in one embodiment, a keypad scan techniquewith radio event isolation comprises a keyscan isolation circuit 10.Keyscan isolation circuit 10, in turn, comprises a keyscan counter 110coupled to a keyscan controller 130. Keyscan controller 130 operates, inresponse to a number of inputs and in a manner described below, toprovide a desired RunScan input signal to a keypad interface device 140.Keypad interface device 140 manipulates the keypad array (not shown inFIG. 1) through output lines KeyOut1, KeyOut2, KeyOut3, and KeyOut4 andinput lines KeyIn1, KeyIn2, and KeyIn3. In this regard, FIG. 2 isprovided as a conceptual representation of the operation of keypadinterface device 140, at least insofar as its operation is germane to anunderstanding of embodiments of the invention. In particular, FIG. 2 ishelpful in understanding the operation of the KeyOut and KeyIn signals.

Referring now to FIG. 2, as may be seen there, a keypad 40 may be viewedas an array of keys. The array may be arranged in (M×N) rows andcolumns. In FIG. 2, M=4 and N=3, but, of course, the invention is not soconstrained. The signals KeyOut1, KeyOut2, KeyOut3, and KeyOut4 arerespectively each coupled to one of the four rows of the keypad array.The KeyIn1, KeyIn2 and KeyIn3 signals are respectively each coupled toone of the three columns. Each node in the keypad array may becorrelated to a key that is identified by a coordinate pair, (R,C). Forexample, in FIG. 2, keypad (3,2) correlates to the key occupying thesecond column in the third row.

Conceptually, the electromechanical operation of a keypad in the arraymay be modeled as a dual-input AND gate. One input to the AND gate isprovided by one of the four KeyOut lines. The second input correspondsto the state of the keypad that occupies position (M,N). That is, ifkeypad (3,2) is activated, then the second input to the AND gate atcoordinate (3,2) becomes effectively a logic ONE, otherwise, logic ZERO.All of the ANDs may then be ORd together, based on the columnarrangement, so that any of the (*,2) ANDs being active, the KeyIn2signal may be activated, provided that the KeyIn is set to pass thisthrough.

As to operation, in a keypad scanning procedure, the KeyOut lines aresuccessively sequentially asserted (e.g., is caused to assume a value oflogic ONE, in some embodiments). As each of those lines is asserted, thestatus of each of the KeyIn lines is sensed. Therefore, assuming key(3,2) is selected, then when KeyOut3 is asserted by keypad interfacedevice 140, KeyIn2 may assume a logic ONE value. KeyIn1 and KeyIn 3 mayremain at logic ZERO. If it is assumed (for pedagogical purposes) that asingle keypad may be activated during the course of a single scan, thenwhen KeyOut 4 is asserted (KeyOut 3 having been deasserted), KeyIn maytransition from logic ONE to logic ZERO.

Returning now to FIG. 1, as seen there keyscan controller 130 is acomponent of keyscan isolation apparatus 10. Numerous implementations ofkeyscan controllers are accessible to persons of ordinary skill in theart. In general, in one embodiment, keyscan controller 130 operates inthe nature of a state machine in response to a number of inputs. In oneembodiment, the inputs to keyscan controller 130 include a FRM Strobeinput 131, a DoScan input 132 from counter 110, and a Debounce Intervalinput 134. In response to the various inputs (and in a manner that willbe revealed below), keyscan controller 110 provides a RunScan output 133to keypad interface device 140 at an input 141.

Keyscan controller 130 implements an appropriate debounce algorithm inorder to reliably and accurately detect keypad activations. When the RFtransceiver is in use, keypad controller 130 will receive periodic FRMStrobe signals at input 131. The FRM Strobe signal is present in anumber of wireless communication standards and/or protocols. Forexample, in GSM or GPRS (General Packet Radio Service), the mobileequipment generates a periodic FRM Strobe signal (pulse). The period ofthe FRM Strobe signal may be, nominally, 4.6 ms. In response, theequipment determines, in general, what activity will be undertakenduring the next sequential frame, i.e., during the next 4.6 ms interval.Accordingly, in response to a FRM Strobe signal received in athen-current frame, the equipment determines events that will occur inthe next frame. The FRM Strobe signal is present when the equipment isactive, i.e., not in a SLEEP mode.

Keyscan controller 130 responds to the FRM Strobe signal as follows. Inone embodiment, keyscan controller 130 causes keypad interface device140 to cycle through all keypad outputs, in the manner described above.If no output presents as activated, then keyscan controller 130 awaitsthe next FRM Strobe pulse. If, however, a key is activated, then theoutput is latched and entered into the state machine. The state machineis also advanced to the debouncing state. When the next FRM Strobesignal is received, that key is again sensed. When the key has presentedas activated a predetermined number of times, as indicated from thedebounce interval delivered to keyscan controller 130 on input 134, thedebounce criteria is deemed to have been satisfied, an interrupt is sentto a system processor.

The number of scan iterations to satisfy the debounce criteria is,generally, programmable, and is defined by the debounce interval input134 to keyscan controller 130. In the example above, two keyscanssatisfied the prerequisite. Note, however, that the number of cycles todebounce typically varies among the different types of equipmentsprovided by numerous manufacturers. In addition, the debounce intervalinput to keyscan controller 130 may also determine whether a keyscan isin fact performed in response to each FRM Strobe signal. With respect tosome keypad designs and technologies, it may judicious to perform akeyscan on alternate, for example, FRM Strobe occurrences.

Accordingly, there has been described above a technique to effectivelyperform keypad scan in a manner that presents minimal, if any,possibility of interference with the RF transceiver subsystem of theequipment. Specifically, keyscan is, in the aspect described above,derived from the FRM Strobe signal, so that a keypad scanning procedureis initiated nearly immediately subsequent to the appearance of a FRMStrobe signal. Because processing associated with the FRM Strobe cannotbe coincident with a radio event (e.g., reception or transmission of aRF signal), then controlling keyscan in this manner necessarily isolatesthe transceiver subsystem from keyscan-related interference. Other timeswithin the GSM/GPRS frame may be equally acceptable for use, however.This time was selected for example purposes, and does not preclude theuse of an independent frame rate signal, occurring at a time differentfrom the frame strobe described.

In another aspect, keyscan isolation circuit 10 also comprises amechanism to enable keyscan to be initiated in the absence of a FRMStrobe signal, as, for example, when the equipment is in a SLEEP mode.Performance of a keyscan procedure in the absence of a FRM Strobe signalis realized through the operation of keyscan counter 110 that, in anembodiment, operates from the 32 kHz clock or real time clock. Ingeneral, when keyscan counter 110 reaches a predetermined rollovervalue, a DoScan pulse is generated at keyscan counter output 111. In oneembodiment, the rollover count may be correlated to the 32 kHz clock orreal-time clock so the counter period approximates the FRM Strobeperiod.

The DoScan pulse at output 111 of keyscan counter 110 is coupled toinput 132 of keyscan controller 130 to precipitate keypad scanning inthe absence of a FRM Strobe signal. During a radio event, thepropagation of the 32 KHz signal clock or real-time clock is interruptedso that counter 110 does not advance. With counter operationinterrupted, the rollover value will not be reached prior to the arrivalof the next FRM Strobe. In order to prevent double scanning the keypad,a FRM Strobe signal is coupled to keyscan counter (Reset) input 113 toalso reset the keyscan counter to zero, the value immediately loadedafter a scan sequence starts.

As seen in FIG. 1, keyscan counter 110 is driven by the 32 kHz real-timeclock. The 32 kHz clock or real-time clock is coupled to a signal input121 of a clock gate 120. Clock gate 120 is controlled by an RIU (radioin use) signal that is coupled to control input 122 of clock gate 120.That is, when the RF transceiver subsystem of the mobile equipment(e.g., cellular telephone) is not in operation, the RIU signal opensclock gate 120. With clock gate 120 open, the 32768 Hz clock signal (orreal-time clock signal) may be coupled from output 123 to signal input112 of counter 110. Conversely, when the RF transceiver is in operation,clock gate 120 closes in response to the RIU signal and interrupts thepropagation of the 32 kHz clock or real-time clock to the counter.

The DoScan output 111 of counter 110 is coupled to input 132 of keyscancontroller 130. Consequently, when the value of counter 130 reaches thepredetermined rollover count, output 111 is asserted (e.g., assumes alogic ONE) and is coupled to input 132 of keyscan controller. The DoScanpulse from counter 110 triggers state-machine cycling of keyscancontroller 130. As indicated above, in one embodiment, the predeterminedcount is correlated to the 32 kHz clock or real-time clock so that, inthe SLEEP mode, the keypad is scanned approximately every 4.6 ms, in amanner that simulates FRM Strobe triggering of the keyscan controller.

The above arrangement conveniently combines two conditions fortriggering a keyscan. Both conditions satisfy the desire to remain“quiet” while using the RF transceiver subsystem.

In an alternative embodiment, the salutory features and advantages of akeypad scan technique (as described above) are preserved, and animprovement in power consumption is afforded. As described above withreference to FIG. 1, with the transceiver subsystem not in operation(that is, in the paging mode or the sleep mode), keyscan occursperiodically, every 4.6 ms, for example, regardless of whether there hasbeen a keypad activation. In the embodiment to be described presently,the periodicity of the keypad scan interval is maintained; however,significantly less power is consumed. In essence, while the mobileequipment is in the SLEEP mode, keypad scans are precipitated when akeypad activation is detected. This technique enables the mobileequipment to assert all keypad output lines and to leave the assertedlines in that condition. Power conservation is realized because theoutput lines are not cycled (asserted and then deasserted) every 4.6 inthe course of repeated scans.

Operation in accordance with the alternative embodiment proceeds asfollows. While performing radio operations, scanning procedure remainspredicated on the FRM Strobe signal. When not utilizing the radiofunctions, i.e. SLEEP mode, the keyscan counter is allowed to reach therollover value. At this point, if no key is currently being debounced,the keyscan counter is interrupted. At the same time, all KeyOut linesare asserted so that a subsequent key activation registers a transitionhigh on a respective Keyln line. For reference, the condition in whichthe keyscan counter is stopped and KeyOut lines are asserted may bereferred to as the wait for press (WFP) state.

While in the WFP state, one of two events may follow that will bring thekeypad block out of the WFP state. The first is to have a key activated.This is easily detected by using an “OR” gate on the KeyIn linesreturning from the keypad array. If a keypress is detected in thismanner, by the “OR” gate going high, the state of the keypad block willbe transitioned to a RunScan state, in the manner described above.Should a scan be performed and no key present as selected, thenfollowing a second interval without a scan detecting a key, present asselected then the keyscan counter is interrupted and all KeyOut linesare again asserted.

A second event that operates to lower the outputs may be the resumptionof radio activity, typically the page operation. Because monitoring thepaging channel causes the frame structure to restart, the FRM Strobesignal may be used to reset the counter. The KeyOut lines will bedeasserted whenever the counter is not at its rollover value. Thus theremay be provided a convenient method of turning off the asserted outputs,without manipulation of the keypad scan block. Once the paging intervalhas passed, the counter will again count up to the rollover value. Uponreaching the rollover value, and not currently debouncing a keypress,the counter will saturate and cause all the keyscan outputs to again beasserted.

FIG. 3 presents a circuit of an exemplary embodiment of a circuitstructure to implement the keypad scanning technique describedimmediately above.

Referring now to FIG. 3, depicted therein is a keypad isolationapparatus 30 that represents an alternative to the embodiment depictedin FIG. 1, for example. As indicated above, the keyscan isolationapparatus of FIG. 3 retains the advantages of the embodiment of FIG. 1,and affords additional advantages with respect to power consumption.

Referring now to FIG. 3, it may be seen there that keyscan isolationapparatus 30 comprises a keyscan counter 110, coupled through CLK gate120 to the 32 kHz clock or real-time clock, keyscan controller 130, andkeypad interface device 140, all arranged largely as shown in FIG. 1 anddescribed above.

In addition, keypad isolation apparatus 30 comprises a logic function300 coupled between keypad interface 140 and keyscan controller 130.Specifically, in one embodiment, logic function 300 comprises an “OR”gate having multiple inputs, 301 a, 301 b, . . . , 301 n (not shown inFIG. 3), coupled to respective inputs from the device keypad. The output302 of OR gate 300 is coupled to input 135 of the keyscan controller andto input 114 of keyscan counter 110.

Note that for purposes of this Detailed Description, OR gate 300 is tobe understood as a pedagogical construct. That is, depending on thetotal number of keypads included in the communications device, OR gate300 may, in fact, be implemented by one or more individual OR gates,each of which has a number of inputs coupled to respective ones of thekeypad outputs. In such an arrangement, the outputs of the individualgates are then combined (logically and/or physically) to provide thedesired output signal. Further, for purpose of this Description, OR gate300 is to be construed as any mechanism that implements the desiredlogic function: activation of any keypad function results in a definedlogical input (logic ONE, for example) to input 135 of keyscancontroller 130. Output 302 of OR-gate 300 is also coupled to input 114of counter 110.

As to operation of the keyscan isolation apparatus embodied in FIG. 3,in the absence of a FRM Strobe signal, the output of the 32 kHz CLK orreal-time clock will be passed to input 112 of counter 110 so thatcounter 110 will count toward a predetermined rollover value, which inpractice closely approximates the frame strobe period. Output 136 fromkeyscan controller 130 is coupled to input 115 of counter 110 to informcounter 110 whether a debounce procedure is then in process. If not,counter 110 will allow its counter to be halted. That is, if keyscancounter achieves the rollover count with no ongoing debounce procedure,counting will be halted. In addition, coincident with the halting ofkeyscan counter 110, a counter output 116 will provide an AssertOutssignal to keypad interface device 140. The AssertOuts output causes allthe KeyOut lines of device 140 to be asserted. The state in which thecounter is halted and all keypad KeyOut lines are asserted may bereferred to as a WFP (wait-for-press) state.

If, during the WFP state, output 143 becomes asserted (suggesting akeypad activation), then counter 110 will again begin to count. When thecounter reaches the rollover value, output 111 will cause keypadcontroller 130 to initiate a debounce procedure such as has beendescribed above. If the apparent keypad activation is not validated inthe course of the debounce procedure, keypad isolation apparatus 30 willreturn to the WFP state.

Subsequently, if operation of the RF transceiver subsystem is resumed(as indicated by the reception of a FRM Strobe signal, for example),then keyscan counter 110 will reset as a result of the applicaiton ofFRM Strobe signal to counter input 113. In addition, resetting counter110 will deassert output 116 from the scan counter 110, which in turnwill cause the KeyOut lines of keypad interface device 140 to againbecome deasserted. That is, by the above-described approach the keypadoutputs may be conveniently deasserted in order to restart RFoperations, without specific direct manipulation of keypad interfacedevice 140. At such time as the RF transceiver subsystem again becomesinactive (i.e., FRM Strobe goes away), counter 110 will continue tocount toward the rollover value. If keyscan controller 130 is not in thecourse of a debounce procedure when scan counter 110 reaches rollover,counter output 116 will go high, thereby causing the KeyOut lines ofkeypad interface device 140 to become asserted. FIG. 4 is a timingdiagram that graphically illustrates the significant signalrelationships encountered in the procedure narrated above.

Referring now to timing diagram FIG. 4, at T₀ a FRM Strobe signal isshown to occur. In fact, in FIG. 4, FRM Strobe may be taken to representthe final FRM Strobe that is received immediately prior to a SLEEPinterval. As indicated above, the occurrence of FRM Strobe means thatthe transceiver subsystem is not in use (i.e., either receiving ortransmitting a signal). Accordingly, a keyscan procedure will beperformed immediately subsequent to FRM Strobe. Keyscan controlleroutputs a RunScan pulse to keypad interface device 140. During theinterval between T₀ and T₁, the keyout lines (KeyOut1, KeyOut 2, KeyOut3, and KeyOut 4) are successively momentarily asserted. Because, in FIG.4 no keys have been activated, during T₀-T₁ none of the KeyIn lines(KeyIn 1, KeyIn 2, and KeyIn 3) are asserted. Similarly, AnyIn Assertremains deasserted during the (T₀-T₁) interval. In one embodiment,(T₀-T₁) may subsume nine periods of the 32 kHz clock (or real-timeclock), that is, approximately 280 microseconds.

At time T₂, the counter reaches the rollover count because there hasoccurred no intervening FRM Strobe signal to reset counter 110. (Recall,saturation is rollover, in the absence of an ongoing debounceprocedure.) Consequently, at T₂ AssertOuts is asserted, as are KeyOut 1,KeyOut 2, KeyOut 3, and KeyOut 4. (Recall that power is conserved bymaintaining an assertion of all KeyOut lines as opposed to sequentially,and repeatedly, asserting and deasserting those lines.)

At T₃, KeyIn1 has been activated. Therefore, AnyIn Assert is asserted,due to the logic OR function. This, in turn causes the counter torollover and to generate a RunKeyScan output, simultaneously. Here, adebounce process, such as has been described above, is initiated, assignified by the assertion of DoingDebounce. Therefore, a keypad scansequence is initiated at T₅ and is completed at T₆. During thatsequence, KeyIn1 presents as asserted. In the next counter-based keyscaninterval, beginning at T₇, KeyOut 2 is pulsed, and KeyIn1 again presentsas asserted.

Persons of ordinary skill in the art will appreciate that the keyscanisolation apparatus described herein may be implemented in numerousways, all within the ken of such persons. For example, the availabletechniques include implementation in the form of combinational orsequential logic, state machines, and ROM (read only memory), to namebut a few. Furthermore, the scope of the invention admits ofimplementation, in whole or in part, by virtue of software programming.

In that regard, it is recognized that embodiments may be realized insoftware (or in the combination of software and hardware) that may beexecuted on a host system, such as, for example, a computer system, aprocessor, a wireless device, or the like. Accordingly, such embodimentsmay comprise an article in the form of a machine-readable storage mediumonto which there are written instructions, data, etc. that constitute asoftware program that defines at least an aspect of the operation of thesystem. The storage medium may include, but is not limited to, any typeof disk, including floppy disks, optical disks, compact disk read-onlymemories (CD-ROMs), compact disk rewritables (CD-RWs), andmagneto-optical disks, and may include semiconductor devices such asread-only memories (ROMs), random access memories (RAMs), erasableprogrammable read-only memories (EPROMs), electrically erasableprogrammable read-only memories (EEPROMs), flash memories, magnetic oroptical cards, or any type of media suitable for storing electronicinstructions. Similarly, embodiments may be implemented as softwaremodules executed by a programmable control device, such as a computerprocessor or a custom designed state machine.

The subject keyscan isolation technique is attractive in numerousapplications. For example, the apparatus may be used with salutaryeffect in a system such as depicted in FIG. 5. The receiving system ofFIG. 5 may be representative in its salient aspects of a radio systemsuch as a cellular telephone or other wireless device such as a personaldigital assistant (PDA), messaging system, and the like.

As illustrated in FIG. 5, system 50 comprises a transceiver subsystem 51that may be coupled, through a duplexer, for example, to a systemantenna. Transceiver system 51 is coupled to a modulator/demodulator 52,which is, in turn, coupled to a baseband stage or circuitry 53. In oneembodiment, baseband stage 53 may be coupled to a keypad 54 through akeyscan isolation apparatus (10, 20) that is configured in accordancewith embodiments disclosed herein. Alternatively, baseband circuitry orstage 53 may be deemed to itself comprise the keyscan isolationapparatus. Keyscan isolation apparatus may conform to the embodimentsdescribed above and illustrated in FIG. 1 or FIG. 3. In an embodiment,and irrespective of which keyscan isolation apparatus is incorporated,the keyscan isolation apparatus may be coupled to a keypad through akeypad interface device 140, such as is illustrated in FIG. 1 and FIG.3.

The disclosed inventive concepts provide many advantages. The inventionprevents keypresses from interfering with radio events, such astransmissions and receptions. It also intrinsically provides for aregular debounce interval, even in the presence of changing radioevents. The change from conventional baseband keypad scanners are tolight the scan lines when it is known that the radio will not be used,debounce based on the frame rate, and efficiently switching betweenradio use and sleep modes, without impacting the scanning method. Whenswitching between frame mode of operation and sleep mode, the scanningmethods are not changed, as the sleep mode debouncing is performed usingthe same time interval as the frame rate.

To save power, the scanning engine provides an all stop operation, wherethe outputs for all keyscan lines are asserted, and the periodicscanning is halted until a keypress is detected or frame mode isrestarted. These transitions are seamless to the scan interval, and thescan engine always operates on a single clock to ease timing closure ofthe design. This automatic change of scan method may ensure that thekeyscan outputs are not asserted while using the radio, and limits theintervention of the local processor to make the keyscan safe for radiouse.

The item for the change between the intrinsic scan and the radioisolation scan is based on the frame rate generation of a scan signal tothe keypad scanner. In the absence of this signal, the intrinsic counterbased scan is performed, or with the lack of a detected keypress, thelow power mode is entered. The pressing of a key or the assertion of theframe signal will transition back from the low power mode into theintrinsic or frame signal driven scanning. There is no concern that anintrinsic scan will occur during frame operations, as the counter thatgenerates the intrinsic scan is disabled while the radio is in use, andthe frame rate signal occurs more frequently than the now extended dueto loss of clock scan interval that the intrinsic counter would provide.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

What is claimed is:
 1. A keyscan apparatus comprising: a keyscancontroller coupled to receive a periodic signal that is provided to acommunications device to establish operation of the communicationsdevice, the keyscan controller having an output to provide a scan signalto couple to a keypad interface device to cause a keypad to be scanned;a counter having a first output and a second output; a keypad activationlogic; wherein in the absence of the periodic signal, the counteroperates in response to the output of the keypad activation logic toprovide a signal at the counter first output that causes the keyscancontroller to provide the scan signal; wherein in the absence of theperiodic signal, the counter operates to provide a signal at the secondcounter output that causes the output of the keypad interface device toassume a predetermined condition; and wherein the keyscan controller isoperative to interrupt a system processor if in the course of a debounceprocedure subsequent to the provision of the scan signal, and inresponse a key is determined to be activated.
 2. A keyscan apparatus asdefined in claim 1, wherein the periodic signal is a frame rate strobesignal.
 3. A keyscan apparatus as defined in claim 1, furthercomprising: means coupled to the keyscan controller for causing thekeyscan controller to provide the scan signal in the absence of theperiodic signal.
 4. A keyscan apparatus as defined in claim 3, whereinthe means comprises the counter having an input to be gated toselectively couple to a clock and having the first output coupled to thekeyscan controller.
 5. A keyscan apparatus as defined in claim 1,further comprising: the counter having a clock input to couple to aclock signal, a reset input coupled to receive the periodic signal, andthe first output coupled to the keyscan controller.
 6. A keyscanapparatus as defined in claim 5, further comprising: a gate having asignal input to couple to a clock, a control input to couple to a statussignal, and an output coupled to the clock input of the counter.
 7. Akeyscan apparatus as defined in claim 6, wherein the first outputcounter is a control signal to the keyscan controller in the absence ofthe periodic signal.
 8. A keyscan apparatus as defined in claim 7,wherein the control signal is related to a predetermined rollover countthat is established in the counter.
 9. A keyscan apparatus as defined inclaim 8, wherein the keyscan controller has an input to couple to adebounce interval signal.
 10. A keyscan apparatus as defined in claim 7,wherein the control signal is related to a programmable rollover.
 11. Amethod of scanning a keypad of a communications device, the methodcomprising: detecting the occurrence of a periodic signal that isgenerated by the communications device to establish an aspect ofoperation of the device; and performing a keyscan procedure in responseto the occurrence of the periodic signal; wherein a counter is coupledwith a keyscan controller and a keypad activation logic; wherein thecounter having a first output and a second ouput; wherein in the absenceof the periodic signal, the counter operates in response to the outputof the keypad activation logic to provide a signal at the counter firstoutput that causes the keyscan controller to provide a scan signalduring the keyscan procedure; wherein in the absence of the periodicsignal, the counter operates to provide a signal at the second counteroutput that causes the output of a keypad interface device to assume apredetermined condition; and wherein the keyscan controller is operativeto interrupt a system processor if in the course of a debounce procedureperformed subsequent to the provision of the keyscan procedure, and inresponse a key is determined to be activated.
 12. A method as defined inclaim 11, wherein the periodic signal is a frame rate strobe signal thatindicates non-operating times of a transceiver subsystem.
 13. A methodas defined in claim 11, wherein the keyscan procedure is performedduring processing of the periodic signal by the communications device.14. A method as defied in claim 13, wherein a keypad debounce procedureis performed substantially immediately subsequent to the occurrence ofthe periodic signal.
 15. A method as defined in claim 11, furthercomprising: performing an alternative keyscan procedure in the absenceof the periodic signal.
 16. A method as defined in claim 15, wherein theperiodic signal is a frame rate strobe signal that indicates operationof a transceiver subsystem.
 17. A method as defined in claim 15, whereinthe keyscan procedure is performed following an alternate control pulse.18. A method as defied in claim 17, wherein a keypad debounce procedureis performed substantially immediately subsequent to the occurrence ofthe alternate control pulse.
 19. A method as defined in claim 15,wherein the alternative keyscan procedure is performed periodically. 20.A method as defined in claim 19, further comprising: coupling a clocksignal to an input of the counter; coupling the first output counter tothe keyscan controller; and coupling an output of the keyscan controllerto the keypad interface device.
 21. A method as defined in claim 20,further comprising: gating the clock signal to the counter input.
 22. Amethod as defined in claim 20, wherein the clock signal is gated by asignal indicative of the state of an RF subsystem of the communicationsdevice.
 23. A method as defined in claim 22, wherein the clock is gatedby a signal indicative of whether a transceiver of the communicationsdevice is operating.
 24. A method as defined in claim 21, wherein thesecond output counter is a rollover indication.
 25. A method as definedin claim 21, wherein the keyscan procedure is originated by a strobelocated within a frame having the same periodicity as the frame ratestrobe signal.
 26. A keyscan apparatus comprising: a keyscan controllercoupled to receive a periodic signal that is provided by acommunications device to establish operation of the communicationsdevice and having an output to provide a scan signal to couple to akeypad interface device to cause a keypad to be scanned; and a counterhaving an input coupled to receive a clock signal, a first output and asecond output; a keypad activation logic; wherein in the absence of theperiodic signal, the counter operates in response to the output of thekeypad activation logic to provide a signal at the counter first outputthat causes the keyscan controller to provide a scan signal; wherein inthe absence of the periodic signal, the counter operates to provide asignal at the second counter output that causes the output of the keypadinterface device to assume a predetermined condition; and wherein thekeyscan controller is operative to interrupt a system processor if inthe course of a debounce procedure performed subsequent to the provisionof the scan signal, and in response a key is determined to be activated.27. The keyscan apparatus defined in claim 26, wherein the periodicsignal is a frame rate strobe signal.
 28. The keyscan apparatus definedin claim 26, further comprising: the keypad activation logic having aninput to couple to a keypad input of the keypad interface device and theoutput coupled to the counter and to the keyscan controller to cause thescan signal to be provided to the keypad interface device in response toa key activation.
 29. The keyscan apparatus defined in claim 28, whereinthe first counter output is a rollover output that corresponds to apredetermined counter value.
 30. The keyscan apparatus defined in claim26, wherein the first counter output is a rollover that corresponds to apredetermined or programmed counter value.
 31. The keyscan apparatusdefined in claim 26, wherein the second counter output causes the outputof the keypad interface device to be asserted.
 32. An article comprisinga non-transitory machine-accessible storage medium comprisinginstructions that, if executed, enable a system to: detect theoccurrence of a frame rate strobe signal; perform a keyscan procedure inresponse to the occurrence of the frame rate strobe signal; and performa keypad debounce procedure within an interval that is relatively shortwith respect to a period of the frame rate strobe signal; wherein acounter is coupled with a keyscan controller and a keypad activationlogic; wherein the counter having a first output and a second ouput;wherein in the absence of the frame rate strobe signal, the counteroperates in response to the output of the keypad activation logic toprovide a signal at the counter first output that causes the keyscancontroller to provide a scan signal; wherein in the absence of the framerate strobe signal, the counter operates to provide a signal at thesecond counter output that causes the output of a keypad interfacedevice to assume a predetermined condition; and wherein the keyscancontroller is operative to interrupt a system processor if in the courseof a debounce procedure performed subsequent to the provision of thescan signal, and in response a key is determined to be activated.
 33. Anarticle as defined in claim 32, further comprising instructions that, ifexecuted, enable the system to: perform an alternative debounceprocedure in the absence of the frame rate strobe signal.
 34. An articleas defined in claim 33, further comprising instructions that, ifexecuted, enable the system to: assert outputs of the keypad interfacedevice in the absence of the frame rate strobe signal.
 35. An article asdefined in claim 34, further comprising instructions that, if executed,enable the system to: establish a state of the system during which theoutputs of the keypad interface device are asserted.
 36. An article asdefined in claim 35, further comprising instructions that, if executed,enable the system to: detect a key activation that occurs during thestate.
 37. A system comprising: a transceiver; a baseband stage coupledto the transceiver; a keypad interface device to couple to a keypad toperform a keyscan procedure on the keypad; and a keyscan isolationdevice coupled to the keypad interface, the keyscan isolation devicecomprising: a keyscan counter having a clock input to controllablycouple to a clock, and a reset input to couple to a system signal thatestablishes an aspect of the operation of the system; and a keyscancontroller having an input coupled to a first output of the counter andan output coupled to the keypad interface device to execute the keyscanprocedure in response to the first counter output in the absence of thesystem signal; wherein the keyscan counter has a second output to coupleto the keypad interface device to cause an output of the keypadinterface device to be asserted in the absence of the system signal; andwherein the keyscan controller is operative to interrupt a systemprocessor if in the course of a debounce procedure performed subsequentto the keyscan procedure, and in response a key is determined to beactivated.
 38. A system as defined in claim 37, further comprising:keypad activation logic circuitry, having an input to couple to a keypadinput of the keypad interface device and an output coupled to thekeyscan counter and to the keyscan controller to cause a scan signal tobe provided to the keypad interface device in response to a keypadactivation.
 39. A system as defined in claim 37, further comprising: aclock gate having an input to couple to the clock, and an output coupledto the clock input of the keyscan counter, the clock gate operable tocontrollably couple the clock to the keyscan counter in response to asignal corresponding to an operating state of the system.
 40. A systemas defined in claim 37, wherein the second output of the keyscan counterto cause an output of the keypad interface device to detect the keypadactivation in the absence of the system signal.